Aqueous coating composition of dialdehyde, a pentaerythritol and half ester and process of insulating wire therewith



formerly necessarytopolyhieriiethe monomeric tea l A: a rocess, required periods 2 ,164,561 r l AQUEOUS COATING COMPOSITION OF DIALDE- A 'HYDEQA PENTAERYTHRITOL AND HALF ES- -':TERL AND PROCESS. OF INSULATING WIRE .-THEREWITHQ- m.- Robert E. Kass, Springfield, Albert H. Markhart, .Wilbraham and Edward Lavim Longmeadow, Mass, assign 'ors" to Shawinigan Resins Corporation, Springfield;

Ma'ss. a corporation of Massachusetts Np Drawing. Filed .Septf26, 1964 S812" No. 58,202

United sees Pawn 3,164,561 .Rate'nted Jan. 5 1965 vention is obvious upon consideration of the elimination of r I a separate polymerization step and its effect upon thecost of the tinalsolid product to the user.

The cured'resin corn-position o f the'present invention is believed tobe the reaction product of the poly'spirane resin and the ouring agent. The cure reaction converts the 'normally 'thermoplastic polyspirane resin to an in- M inventionpertainsto the preparationof'aqueous coating compositions 'comprisingireactive organic compounds which yield polymeric condensation products that are especially suitable for electric andthermal insulation;

More particularly, this invention pertains foo-the preparation of aqueous solutions containingcertaindialdehydes andfpolyhydric alcohol reactants; which reactants when condensed in situ andfurther cured according. tqthemethod hereinafter described form crosslinked resinous products having unexpectedly useful properties. 7

- It is known generally to condense dialdehydesjwith.

fusible crosslinked rnaterialhaving greatly improved chem ical; thermal and jrnechanicaljstability; Although the applicant's do not desire to be limited by any theoretical consideration of the cure reaction, it is believed that the monomeric dialdehyde and pentaerythritol materials .first condense during the reaction under the influence of heat and the acidic nature Ofthe W agent nd thereafter furt her polymerize. the heating is continued, it is believed that the half-ester cure agent is next converted to the original anhydride material from which the half-ester is'p repared;

which ahhydride thereafte'r'proceeds to crosslink the conduring'the'practice'of the invention can be represented r n ae y i tu-q na ne q y pi n r si ns ha as taught in'Australian Patent 225,640. The-knowncondens ates are thermoplastic polymers, however,,whi ch are generally too low in molecular weight torgoptinrump r mechanical properties. It is also knownto preform the i1P9 YPim J a hymenad mQ Qratine particular curing agentsin the rsystem,e;g,;.coating corn posit-ions,-to thereafter crosslink the pol-yspirane to obtain cured solid products having eigcellentjtherrnal and-chem r ar stability. :Anaqueousflispersion form of the lattef system is disclosed by the applicants in-their-copending,

application Serial Number 797 016, mealanaar -4, 1959.

(issued as US. ra e tgsjnssgss on Novel Illoer 11 3,1 962) ItFhas .now been found.unexpectedly, that an a quecn s coating composition comprising a solution of adialdehyde a pentaerythritoland the haltester. reaction product of alcohol a polyca rboxy cyclic anhydridematerial se lec ted from the. group consisting oflanh'ydrides and: diaiihydrides ,canbe. cured to form solidsproducts having properties substantially equivalent'to the. known gprepoly rner compositions, That theproperties of the cured monomeric compositions aresub'stantially equivalent t o those; of thecuredgsystemrof a p olyspiraneresin an 4 agent is surprising inview otthe possibility of n'desirable reaction. betweenlthefcuring agent and the monomeric .re-T.

actant's in the coating compositionpriof to the react-ion'of "the latter materials to fOrm-a linear polyspirane polymer.

In addition,.the.applicants havenow found that the same type of curing method heretofore employed solely to cross-.

,a system comprising the polyspirane resin and the crosslinking agent may now. be. employed to efiect the.

polymerization of the monomericreactantsg'as' achieveflie' c'iosslinking reaction; 'Mor'especiiically,

prior to crosslinking by exe iii a li whine ainaertwifa. a t ge molecular weights generallyin excess of 700,

the subsequently cross'linked producttohaveihe desired chemical and thermal order tor bility. It has now. been ground,

mulae:

densation polymer already formed. I

' Theparticular polyspirane resin that is believed formed as--having recurring units iofthe following general forwhereR is 'taken from" the group consisting of aliphatic hydrocarbon radicals. definedby .(CH' where S is a n integer from 2 -4 and alkyl-and hydroxyl substituted products thereof. lheratio of x to y in'the above general for mula 'is dependent upon-the relativ e proportions of monopentaerythritol and dipentaerythritol in the coating composition. The dialdehydeeomponent of the resin can be selected firomthe group consisting of -succinaldehyde,

glutaraldehyde, hydroxyadipaldehyde, and mixtures there: of. The pentaerythritol component-of thepolyspirane condensation product canbe monopentaerythritol, dipentaerythritoL'or' mixtures thereof. The acceptable ratio for thefiialdehyde and pentaerythr-itol components in the aqueous coating composition of the invention i-sl-Z moles dialdehytieaiid 11 2 nflols pentae'rythritol. Approximately eguimolar aniouiits of-the dialdehyde-and pentaerythria tol in {the aqueous coating compositionhavefbeentqulid to produce the best results} h'er polypentaer cured icorhpdsitibiig, onwdepending on reaction conditions, ,canl' "significantly increase the degree or ease of 5 erossl'inking. However, the use o f over} 50% dipentaehowever, that substantially the same-degree pt the aqueous monomeric composition previously menrequiring a .few 'minutes'at' most. The 'utility of the I h i ol-(base on t ewe h f th p ta ty ito can 'also lead, to products possessing increased water-sen:

sitivityvor decreased chemical or heatstability. 1V

. l The invention. is practiced in its. preferred embodimentwas illustrated inthe following examples but is notliinite'd thereto. .Whenever, inthe specificationand'claimsgirefer'nce isnfade to parts and percentages, the referenceisto parts and percentages by weightunless otherwise" .the' monopentaerythritol aindrdipentaetives thereof are alsQLusable as .well I V ythrit'ols. The usei'of about 81% or, q "dip enta'erythritol (by weight offthe. total pentae rythritol) can add 'a greaterdegrgee offflexibility to the constituted the final coating composition.

Q fAWG lii magnet wire by means of passin'g'the wire verticallythrough a container of the coating composition at approximately 18 ft./min. travel speed and thereafter I in thousandths of an inch is the'build and is measured I gated approximately "25% simplyi by lclamping the speci the stretched.specimen is wound around circular man drels-whose'diameters are 1, 2 133 timesthe, diameter V the stretched specimen may be wound for 1 0 turns withouti'cracks or ruptures' is; reportedL 1 1 and .flexi bilityof the curedfilm to :th'eimetal wire and is made in aecoiq ncewith ASA (American S tanda'r'd s 1 Association)specifications, wherebyja's'a rri'ple of the curedcoated wire is elongated to failure of the wire at anelon I the test if no craclcs or. lossofadher'ence appear inthe 'cQatin'gmor e'than' /s inch fromthe break after the test.

ducted on a'standard testefidentifiable as Twist Counter "1 Model (Scott Testers); whereby-a straightsection' i .34 0f coated wire l'is clamped onboth ends and thereafter twisted manually. .Ilfhei number of twists beforewhich thelcoating separates from the wire is'frecorded.-v Abrasiofiresistanc.:Abrasion resistance is determined by iaj'National Electrical Manufacturers Association"Test f whichconsists of repeatedly fs'crapingthe surface, of thee wireuntilithe enamel is worn through. Aweight of 700 Y 90'parts of technical .pentaerythritoLwhich a mixtui'e of...88 parts by, weight of the mixture. of monopentaerythritol. and 12 pa'rtstb'y weight'of the mixture of dipentaerythritol was dissolved in 263- parts' of a 25% aqueous solution of glutaraldehyde to which lOOparts of excess water'has been added. The pentaerythritol was dissolved by simply stirring the mixturewhich'had been.

heated to 90-96? C. The clear'solution was then cooled to room temperature. P 1' Solutioir it i .;1227 parts oithe diethyl ester ofpyromellitic acid were I dissolved in a mixture of 29 parts ethanol and -5 l;.parts acetone. A clear solution resulted. I Solutions A- and B were then mixed at room temp 653- ture to give a clear,-faint yellow solution which mixture j The above coating composition was'next ,dip applied to passing the coated wire througha 12 ft..longconventional type fwire enamel tower. operated at 390 ?"C.,' where q the coating is' dried and heat-cured to form a crosslinked'j film having theproperties shown inTable I below: a 'T'ABLEI.v Property: 3 i I I i i g 7 Value:-

I Build, mils 3.0. Wrap test for flexibility ,1: Jerk test passed.

Axial twist test 96. i Abrasion scrapes (700 gram load) 55. E Dielectriclife (1 kv;.atj200 C. hours i before failure) '452. 40 Cut-through temperatureiC'C.) 210'. .1 LHeat shock test-(160 C., l hour) 1 diameter;

Dielectricstrength(volts/mil) 2000;. v Monochlorodifiuoromethane extracti- 1 .bles (wt. percent) .:-O.53

Build. The addition to the diameter of the bare wire,

by-meansof a micrometerfcaliper. Q v

Wrap zest for flexibilityF-Thecoated wire is first elonmen at both ends and pulling apart'slowly. Thereafter,

of. the coated wire. Thesmalle'st 1dia1neter;;a boutwhich" Jerk tcst.,Thejerk test isa' measure of the adherence 7 gation rate of l2- lj 6 feet'per second. "The sample passes coatingfwith a rigidfsteel needleat a right angle tothe;

grams is used to press the needle against the coating and the number of strokes, required to scrape through the coating is considered the abrasion resistance;

' Dielectric life test-This testis a measure lengthof time for which the coating can be exposed at the particular temperature indicated before it will fail as electrical insulation upon theapplication of volts on e the-sample. The test, measurements are made in accordance with the provisions of A.I.-E.E. (American Institute of Electrical Engineers) Specification No. 57, 'datedOctober 1 955.? The; test results are reponted as the number of hours before failure for the particular test specimens. Cut-through;tentperatzkra+To1 determine the cutthrough temperature specimens. of'the coated wire are crossed at 90 and a load of five pounds placed atthe junction. The temperature is raised at a rate of 10"; C. per minuteuntil electrical short circuiting' at the une-- tion closes an indicator circuit thereby determining the cut-through temperature,

H eat shoc'k' test r-Heat shock is defined as the cracking of a stressed wire ,coatingwhen heated. The test is conducted on specimens'which have been wound for '10 turns around circular mandrels whose diameters are'l, 2

or 3 times the diameter of the wire. 'Next the wound specimens-arefplaced' in a mechanical-convection oven heated to C. for one hour, thereafterremoved, and examined-when cool. j The smallestmandrel overwhich no cracks have developed is reported. I

- Dielectric strength..f-The dielectric strength of the coat-v ing is measured by an A,S.A. procedure'whereby the'voltage at which the electricalfailure'between a pair of twisted coated Wires occurs is reported on a per unit thickness of the coating basis. l

' Moh qchlorodifluoromethane ous refrigerant infa liquid state,jand the test conditions .in the bomb 3.1'61205-240 p.s.i. and 37-43" C. The test specimens are removed after the immersion period, dried and re-weighed. The amount of extractibles' obtained from the 'coating is. thereafter calculated on a percent 'weight loss basis. t

To illustrate the preparationof other aqueous coating compositions within the contemplation of the invention, Examples 2-6 are shown. The function'i of a water- I soluble hyd 'ophilic colloid in the coating composition .is toincrease the thickness'of liquid coating appliedfto the lwire by the method of- Example 1. Examplef6' also illustrates the use of ajwater-soluble salt inthe coating composition which salt promotes the cure reaction.

I .EXAMPLE12 thev following compositions aqueous coating composition was: prepared having 2 hydroxyadipaldehyde (25 %"aqueou's*solution')' l 960 Technicalpentaerythritol HydroXyethylcellulos'e, l' 6 I The properties of the cured prepared fromithe above composition according to the method of' Example 1 were substantially companablefto .t'hepr openties obtained for saidfExaniplefl.

Diethyle'sterof pyromellitic acid 22% solids'ethanol acetone solution) Water of the to the said' aqueous solution is believed to I lent method offpreparation. r

- 7 ferred' concentration of the cent by weight, or about 0.2 to 7.5%based on the total combined weight of the dialdehyde and pentaerythritol. The anionic portion of the cure. promoter is preferably selected from the group of weak acids, for example, acetic and boric acid. I I

The method ofpreparation of the aqueous coating cure promoter the coating. compositions of the present invention is 0.1 to 1.0 per-' 'final product are needed,-

others. 7 v w In addition to the various applications for the present compositions 'hereinbefore described, it will be obvious to those skilled'in the art that not only other applications are apparent but other compo'sitions and other processes for the manufacture of the compositions are likewise 7 within the scope. of this invention. i

compositions of the invention is not believed critical. As.

has been shown in Example 1, simple mixing of the corhponents 'of'the composition at moderately elevated temperatures produces a clear solution.

Further, while it is preferred to use a two step processof adding an organic liquid solution of the curing agent to the aqueous solution of the monomeric reactants, thedirect addition of a readily water-soluble curing agent he an equiva- What is claimed is:

1. An aqueous coatingeomposition comprising (A) an,

aqueous solution of (.1) p a dialdehyde selected from the groupconsist-ing of glutaraldehyde, succinaldehyde, hy-

.' droxadipaldehyde and mixtures. thereof, =and (2) a pentaerythri-tol selected. from. the group consisting of. monopentaerythritol, dipentaerythritoland mixtures thereof, in

which solution the dialdehydef and pentaerythritol. are

present in the ratios of 1-2 moles dialdehyde a-nd 1-2 The curing temperature, for the presentcompositions islimited by the temperatures at which the acid-ester curing. agent employed will crosslink the polyspirane resin formed fromthe'monomeric reactantsof the composition during" the'heat cycle. Theminimum cure temperature has been found to be approximately 200 C. which is: the "temperature' required for the-acid-ester curing'agents used-to regenerate th 'anhydridematerial which crosslinks the poly-.

spirane. :Other'factor's such as the type ofcuring' equip- .ment used and desired time to complete the cure reaction" will influence the optimum cure temperature;selected;- v .For the compositions in the preceding example's a stand-f;

ardlcommercial typewire enamel jtower Wasutilized,- wherein operating temperatures of 300 450 IC. were employed. However, curing at temperatures up at 600 C. J

are feasible ifthe curing time is kept toa minimum.

1 he thickener used in the aqueous coating compositions may be other hydrophilic colloids'than the hydroxyethyL' moles, pentaerythritol, and (B) ,a half-ester reaction productof an alcoholfwith a polycarhoxylic cyclic anhydride material selected'from the group consisting of anhydrides and dianhydrides, in which coating' composition the halfester is present in the amount of 1- -3 0% of the total combined weight of the dialdehyde and pent'aerythritol, said alcohol being selectedtromthe group consisting of methyl alcohol, ethyl alcohol, and aliphatic diols and triols having 2-8 carbon atoms, and said anhydride material being selected from the-group consisting of pyromellitic anhydride, methyl succinic -anhydride, m-aleic anhydride and hexachloroendomethylene.tetrahydrophthalic anhydride.

cellulose'usedin the examples aslongasthc material is L compatible with the coating composition and thefilms,

positions.

21K composition -as inhclaim 1 wherein. the half-ester is soluble in watenq '3. A composition as in claim 1 wherein the half-ester. uis'l dissolved in a volatile' water-miscible, organic solvent.

4. A composition as in clairnl 'wherein the anhydride material is pyrom ellitic anhydride. i 5. [An aqueous coating compositi also contains a thickener.

6. An aqueous coating 'composition'as in claim 1 40 wherein thedialdehyde is glutaraldehyde;

7. An aqueous "coating composition as in claim 1 wherein the dialdehydeis Z-hydroXyadipaldehyde. V

An aqueous coating composition as inclaim 1.

wherein the dialdehydecomprises a mixture of .Z-hydroxy- 1Th e total solids. of the aqueous coatingcompositions will generallybe determined by the viscosity desired, dry- 1ng conditions and by the filmthickness or other characteristics required The amount" of reactants will generallyrange from about 1-0=to.50% by weight" of the composition; r i It 'is to be understood that this invention isfnot limited adipaldehyde with 2,5-dimethyl{2-hydroxyadipaldehyde.

V wherein the-pentaerythritoi comprises amixture of monoj pentaerythri-t'olv with dipentaeryth ritol containing" aboutv 9. An aqueous coatingf'composition as in claim. 1

88 parts of monopentaerythritol and about 12 parts dipentaerythritol by weight ofthe mixture; V

to the particular wirev coatings disclosed'in the above examples. It isobvious" from the above test results that 'a wire coated with the present composition-alone would .be acceptable as Class B service wire. But it is also ohviou'stothose skilled in the art to modify the application.

of the resin composition so as to upgrade the high-temperature usefulness of the coated wire by means of known practices in the field. It is possible for instanceto utilize the present coating as an undercoat on .a wire and to apply as an overcoat one or more of the many compatible insulating varnishes and, thereby. obtain a coating acceptableas a Class For higher insulation. It is also notintended to limit the'application of the present compositions as electrical'insulation ffor wire merely. For example,

the present compositionscan also be used as an adhesive agent inthe bonding oit electrical parts for expected use at elevated temperatures. .Eurther use canbe made of the inyention compositions as insulation and/or. impregnat .ingvarnislie's for such articlesas glasstapes or electrical coils. O'the'r' non electricalu'ses of this resinare apparent where chemical resistance and1teiriperature stability' of the f -10. An aqueous coating composition "comprisinga: solution of (1) about equimolar amountsof adialdehyde selected from the:' group consisting oigluta'raldehyde, succinaldehyde, hydroxyadipaldehyde and mixtures :thfil'60f with a pentae'rythritol selectedi-r'om the group consisting of inonopentaerythritol, dipentaerythritol and mixtures thereof; and (2 ahalf-esterjreaction product of an alco- 1101 with a poly c'arboxylic cyclic anhydride material selected from the group consisting of ,anhydrides and di anhydrides; in which coating compositionthe half-ester is present the amount of l3.0% ofthe'totalcombined' weight of the dialdehyde and pentaerythritol, said alcohol being selected from the group consisting of methyl alcohol, ethyl alcohol, andxaliphatic diolsand triols having- 21-8 carbon .atoms, said anhydride material being selected from the group consisting ot'pyromellitic anhy dride, methyl succinic anhydride, maleicanhydride and hexachloroendomethylene tetrahydrophthalic' anhydride.

11. vAnaqueous coating composition. as inclaim 10 containing a volatile, water-miscible, organic solvent for the half-ester.

'12. 'An aqueous coatingcomposition as in claim 10 whereinthe anhydride material pyromelli-ticanhydride.

which also contains a thickenen'} 13. An aqueous:

eating-composition as in claim 10 such as surface coatings and on a's in lwhich 14. An aqueous coating composition as in claim wherein the dialdehyde is glutaraldehyde.

15. An aqueous coating composition as in claim 10 wherein the dialdehyde is 2-hydroxyadipaldehyde.

16. An aqueous coating composition as in claim 10 wherein the dialdehyde comprises a mixture of Z-hyd-roxyadipaldehyde with 2,5-dimethyl-2-hydroxyadipaldehyde.

17. An aqueous coating composition as in claim 10 wherein the pentaerythritol comprises a mixture of monopentaerythritol with dipentaerythritol containing 88 parts monopentaerythritol and 12 parts dipentaerythritol by weight of the mixture.

18. A process for the manufacture of a solid resinous product comprising heating at a temperature of about 200 to 600 C. of an aqueous solution comprising (1) a dialdehyde selected from the group consisting of glutaraldehyde, succinaldehyde, hydroxyadipaldehyde and mixtures thereof, (2) a pentaerythritol selected from thegroup consisting of monopentaerythritol, dipentaerythritol and mixtures thereof, and (3) a half-ester reaction product of an alcohol with a polycarboxylic cyclic anhydride material selected from the group consisting of anhydrides and dianhydrides, for a sufiicient period to remove the water and cure the resinous product formed, said alcohol being selected from the group consisting of methyl alcohol, ethyl alcohol, and aliphatic diols and triols having 2-8 carbon atoms, and said anhydr-ide material being selected from the group consisting of pyromellitic anhydride, methyl succinic anhydride, maleic anhydride and hexachloroendomethylene tetrahydrophthalic anhydride.

19. A process for insulating an electrical conductor comprising coating the conductor with an aqueous solution comprising (1) a dialdehyde selected from the group consisting of glutaraldehyde, succinaldehyde, hydroxyadipaldehyde and mixtures thereof, (2) a pentaerythritol selected from the group consisting of monopentaerythritol, dipentaerythritol and mixtures thereof, and (3) a halfester reaction product of an alcohol with a polycarboxylic cyclic anhydride material selected from the group conremoving the water and curing the coating at elevated temperatures of about 200 to 600 C., said alcohol being selected from the group consisting of methyl alcohol, ethyl alcohol, and aliphatic diols and triols having 2-8 carbon atoms, and said anhydride material being selected from the group consisting of pyromellitic anhydride, methyl succinic anhydride, maleic anhydride and hexachloroendomethylene tetr-ahydrophthalic anhydride.

20. A process for insulating wire which comprises coating a bare metal wire with an aqueous solution comprising (1) a dialdehyde selected from the group consisting of glutaraldehyde, succinaldehyde, hydroxyadipaldehyde and mixtures thereof, (2) a pentaerythr-itol selected from the group consisting of monopentaerythritol, dipentaerythritol and mixtures thereof, and (3) a half-ester reaction product of an alcohol with a polycarboxylic cyclic anhydride material selected from the group consisting of anhydrides and dianhydrides, and thereafter simultaneously removing the water and curing the coating on the wire at a temperature of about 200 to 600 C., said alcohol being selected from the group consisting of methyl alcohol, ethyl alcohol, and aliphatic diols and triols having 2-8 carbon atoms, and said anhydride material being selected from the group consisting of pyromellitic anhydride, methyl succinic anhydride, maleic anhydride and hexachloroendomethylene tetrahydrophth-alic anhydride.

References Cited by the Examiner UNITED STATES PATENTS 2,785,996 3/57 Kress 26067 3,015,643 '1/62 Markhart et a1 117 232 3,063,955 11/62 Kass et al 260-67 OTHER REFERENCES Bjorksten: Polyesters and Their Application, Reinhold Publishing Cornpauy, New York, pages l67and 168.

D. ARNOLD, Primary Examinenj LEON J. BERCOVITZ, Examiner. 

1. AN AQUEOUS COATING COMPOSITION COMPRISING (A) AN AQUEOUS SOLUTION OF (1) A DIALDEHYDE SELECTED FROM THE GROUP CONSISTING OF GLUTARALDEHYDE, SUCCINALDEHYDE, HYDROXADIPALDEHYDE AND MIXTURES THEREOF, AND (2) A PENTAERYTHRITOL SELECTED FROM THE GROUP CONSISTING OF MONOPENTAERYTHRITOL, DIPENTAERYTHRITOL AND MIXTURES THEREOF, IN WHICH SOLUTION THE DIALDEHYDE AND PENTAERYTHRITOL ARE PRESENT IN THE RATIOS OF 1-2 MOLES DIALDEHYDE AND 1-2 MOLES PENTAERYTHRITOL, AND (B) A HALF-ESTER REACTION PRODUCT OF AN ALCOHOL WITH A POLYCARBOXYLIC CYCLIC ANHYDRIDE MATERIAL SELECTED FROM THE GROUP CONSISTING OF ANHYDRIDES AND DIANHYDRIDES, IN WHICH COATING COMPOSITION THE HALFESTER IS PRESENT IN THE AMOUNT OF 1-30% OF THE TOTAL COMBINED WEIGHT OF THE DIALDEHYDE AND PENTAERYTHRITOL, SAID ALCOHOL BEING SELECTED FROM THE GROUP CONSISTING OF METHYL ALCOHOL, ETHYL ALCOHOL, AND ALIPHATIC DIOLS AND TRIOLS HAVING 2-8 CARBON ATOMS, AND SAID ANHYDRIDE MATERIAL BEING SELECTED FROM THE GROUP CONSISTING OF PYROMELLITIC ANHYDRIDE, METHYL SUCCINIC ANHYDRIDE, MALEIC ANHYDRIDE AND HEXACHLOROENDOMETHYLENE TETRAHYDROPHTHALIC ANHYDRIDE. 